html,body{
    padding: 0;
    margin: 0;
    height: 100%;
    width: 100%;
}
#BG{
    height: 100%;
    width: 100%;
    min-width: 960px;
    min-height: 700px;
    background-image: url("../img/loginbg.jpg");
    background-size:100% 100%;
    position: relative;
}
#Login_Div{
    margin-top: -165px;
    margin-left: -250px;
    position: absolute;
    width: 500px;
    height: 330px;
    border-radius: 10px;
    top: 50%;
    left: 50%;
    background: #fff;
}